Driving devices for loom shed-forming mechanisms

ABSTRACT

A device to be inserted between a loom and its shed-forming mechanism to permit of rotating the latter backward or forward independently of the loom when required and thereafter to resume normal weaving with proper timing of the mechanism with respect to the loom, comprises a rotating member connected with the loom so as to effect one revolution for each pick thereof, a singletooth clutch to connect this member with a main shaft connected with the shed-forming mechanism, during normal weaving, and coupling means to connect the said main shaft with a gearing adapted to rotate this shaft by successive complete revolutions. These coupling means include a first element rigidly carried by the said shaft, and a second element which may be engaged with or disengaged from the first one. The gearing comprises a driving gear wheel having a toothed sector and a smooth blocking sector, and a corresponding pinion having a toothed sector and a concave depression to receive the smooth blocking sector. The pinion is affixed to the second element of the coupling means, while the gear wheel is carried by an auxiliary driving shaft connected with an appropriate auxiliary motor, and this shaft carries cams adapted to control the single tooth clutch and the coupling means. When the auxiliary motor is started, during a first step the second element of the coupling means is blocked by the smooth sector and the cams disconnect the main shaft from the rotating member and connect it with the second element of the coupling means. During a second step the toothed sectors cooperate to rotate the main shaft through one revolution. Then during a third and last step, the smooth sector again blocks the pinion and the second element of the coupling means, while the cams reestablish the initial connections.

United States Patent Fumat [54] DRIVING DEVICES FOR LOOM SHED- FORMING MECHANISMS [72] Inventor: Joseph Fumat, Lyon, France [73] Assignee: Verdol S. A., Rhone, France [22] Filed: Feb. 22, 1971 [21] Appl.No.: 117,303

[30] Foreign Application Priority Data Mar. 9, 1970 France ..7008259 [52] U.S.Cl ..139/1E [51] Int. Cl. ..D03d 51/00 [58] Field ofSearch.. ...139/1, 1 E, 55,336,317, 329

[56] References Cited UNITED STATES PATENTS 2,421,539 6/1947 Clarke ..l39/l E 3,405,740 10/1968 .Iuillard.. 3,557,841 1/1971 Moessinger ..139/1 E Primary Examiner-Henry S. .laudon Att0rneyAleXander & Dowell 5 7] ABSTRACT A device to be inserted between a loom and its shed-forming mechanism to permit of rotating the latter backward or forward independently of the loom when required and thereafter to resume normal weaving with proper timing of the mechanism with respect to the loom, comprises a rotating member connected with the loom so as to effect one revolution for each pick thereof, a single-tooth clutch to connect this member with a main shaft connected with the shed-forming mechanism, during normal weaving, and coupling means to connect the said main shaft with a gearing adapted to rotate this shaft by successive complete revolutions. These coupling means include a first element rigidly carried by the said shaft, and a second element which may be engaged with or disengaged from the first one. The gearing comprises a driving gear wheel having a toothed sector and a smooth blocking sector, and a corresponding pinion having a toothed sector and a concave depression to receive the smooth blocking sector. The pinion is affixed to the second element of the coupling means, while the gear wheel is carried by an auxiliary driving shaft connected with an appropriate auxiliary motor, and this shaft carries cams adapted to control the single tooth clutch and the coupling means. When the auxiliary motor is started, during a first step the second element of the coupling means is blocked by the smooth sector and the cams disconnect the main shaft 8 Claims, 6 Drawing Figures fi l 5 if". 1

PATENTEDMM 9:972 $661,185

SHEET 2 0f 2 F, INVENTOR. I 3 w DRIVING DEVICES FOR LOOM SHED-FORMING MECHANISMS The present invention relates to a device adapted to realize a connection between a loom and the shed-forming mechanism associated therewith.

A shed-forming mechanism, such as a jacquard or a dobby, should of course operate in accurate synchronism with the loom so as to open the shed at the proper time for passage of the shuttle or other weft inserting means, and thereafter to close it in time for operation of the slay. With modern jacquards or dobbies which comprise a rotating shaft, this may be easily obtained by connecting this shaft with the shaft of the loom by means of a chain. But this quite simple solution has the disadvantage that when it is necessary to remove some weft threads, as for instance to eliminate a defect in the fabric, the loom should be run backwards without the shuttles, pick after pick, each weft being removed during each stoppage between two successive picks. Such an operation is tedious and time-consuming. The sudden successive stoppages and restartings are detrimental to the motor and to the loom gearing. They considerably increase the wear caused to the warp threads by the beating reed which slides three times more against them (once during the former normal weaving, once more during backward operation of the loom and once again when normal weaving is resumed). It has been proposed to avoid this inconvenience by de-clutching the shed-forming mechanism form the loom and to remove the wefts by merely rotating this mechanism backward while the loom remains at standstill.

The same problems arise when it is desired to advance the shed-forming mechanism with respect to the loom, as for instance when a portion of the pattern is to be omitted, or to correct an error in the timing of the said mechanism.

But this de-clutching of the shed-forming mechanism with respect to the loom raises a difficulty, namely the obtention of the proper timing when normal weaving is to be resumed. In practice when a loom is stopped it is automatically blocked by a strong brake together with the shed-forming mechanism which is positively connected therewith. But as soon as this mechanism is de-clutched from the loom its shaft is free to rotate under the action of the reaction of raised hooks on the corresponding knife frame. This causes a slight angular difference which should be taken into account when re-clutching the shed-forming mechanism with the loom, in order to avoid an error of one pick in one or the other direction. It is known to obviate this disadvantage by blocking the shed-forming mechanism at the same time as it is de-clutched from the loom, more particularly by clutching this mechanism with an individual driving motor combined with an automatic brake. With such an arrangement the shed-forming mechanism may be rotated by successive picks in any direction and be thereafter re-clutched with the loom exactly as desired and without any risk of error due to self rotation of this mechanism. Moreover in order to correct any minor angular difference between the shaft of the mechanism and the shaft of the loom, it is customary to use a clutch having a single tooth on each of its elements, which only permits a single relative position between both shafts.

It is an object of the present invention to provide a device which will effect in a wholly automatic manner the successive elementary operative steps required to rotate a shed-forming mechanism backward or forward independently of the loom with which it is associated, while ensuring proper timing when the loom is re-started.

The device according to the invention is of the kind comprising a single-tooth clutch adapted to connect the shaft of the shed-forming mechanism with a first member driven by the loom and coupling means which may connect this shaft with a second member driven by an auxiliary individual motor combined with an automatic brake, and it further comprises an auxiliary driving shaft connected with the auxiliary individual motor in such manner as to rotate through one full revolution and only through one revolution each time this motor is started by the operator in one or the other direction, a first rotatable unit of toothed drivingsector and of smooth blocking sector keyed on this auxiliary shaft, a second rotatable unit of toothed driven sector and of arcuate blocking depression to cooperate with the said first unit in such manner that for each revolution of the auxiliary shaft this second unit may be rotated through a full revolution, but while starting with a given delay with respect to the auxiliary driving shaft and while stopping with an advance substantially equal in time to the said delay, coupling means interposed between the said second unit and the shaft of the shed-forming mechanism, and a pair of cams carried by the auxiliary driving shaft to actuate the single-tooth clutch and the coupling means in a first direction during the said time of delay and in the reverse direction during the said time of advance.

It will be understood that during the delay the second unit cannot rotate, since it is retained by the smooth blocking sector of the first unit keyed on the auxiliary driving shaft. Meanwhile the cams carried by the said shaft may freely connect the shaft of the shed-forming mechanism with the second unit and de-clutch this shaft from the member driven by the loom without the said shaft being free to rotate at any time. The toothed sectors of both units then come into engagement and the shaft of the mechanism is rotated through one full revolution. Then during the time of advance, the cams may act to reestablish the initial connections thus enabling the operator either to resume normal operation of the loom together with the shed-forming mechanism, or to re-start the individual motor in order to again rotate the said mechanism through one revolution independently of the loom.

Since the device is entirely symmetrical concerning the times of delay and of advance, it may be operated in any direction or in other words the shed-forming mechanism may be rotated either backward or forward if desired.

The coupling means preferably comprise a toothed clutch having a relatively large number of triangular teeth and in the single-tooth clutch the sides of the tooth have an obliquity which, as seen from the axis of the clutch, extends through'an angle substantially equal to half the pitch of the teeth of the multiple tooth clutch, in such manner that the latter may always be brought into engagement while the former is disengaged and vice versa. Moreover in order to eliminate .any difficulty in the engagement of the multiple tooth clutch due to the teeth thereof abutting against each other exactly by their tips, there is preferably provided on one of the elements of this clutch an axially slidable centering tooth loaded by a spring so as to protrude beyond the other teeth of this element. When the clutch is actuated, if the teeth of both elements are exactly facing each other, this protruding tooth is the first to come into contact with the tip of a facing tooth and it may slide freely along one or the other of the sides thereof, thus causing .a slight relative rotation of both elements and eliminating any risk of jamming.

Finally in order to taken into account the possibility that the tip of the centering tooth might remain applied against the tip of the facing tooth instead of sliding laterally, this centering tooth may be very slightly displaced angularly with respectto the other teeth, whereby in such a case the said other teeth of the same element are not exactly in front of the teeth of the other element and slide against one of their lateral sides, thus causing a slight relative rotation of these elements and disengaging the centering tooth. In the annexed drawings FIG. 1 is a general longitudinal section of a device according to the invention FIG. 2 is a diagrammatical view of the speed-reducing gearing interposed between the auxiliary individual motor adapted to drive the shed-forming mechanism independently of the loom FIG. 3 is an end view corresponding to the left-hand side of FIG. I

FIG. 4 is a large scale sectional view illustrating the centering tooth and its associated parts 7 FIG. 5 is a developed diagram showing the action of this centering tooth FIG. 6 illustrates the electric circuitry of the device.

The device illustrated in FIG. 1 comprises a main shaft 1 on which is keyed a bevel pinion 2 adapted to mesh with a corresponding bevel wheel carried by the shaft of the shed-forming mechanism (not illustrated), this wheel being shown in phantom lines at 3. In order to simplify the explanations it will be hereinafter supposed that this mechanism is a jacquard, as for instance of the Verdol type. Shaft 1 is rotatably supported and axially retained by anti-friction bearings 4 and 5 mounted in parts 6 and 7 of the frame of the device, this frame being preferably rigidly secured to the frame of the jacquard.

Shaft l carries a tubular shaft 8 which is rotatably supported thereon by linings 9, its axial displacement being prevented by a ring 10 pinned to shaft 1 and by a washer 11 also secured to the said shaft. Shaft 1 is positively connected with the loom in any appropriate manner so as to effect one revolution for each pick thereof. This connection may be effected in the conventional manner by means of a sprocket wheel and of a chain, as indicated in broken lines at 12 and 13.

The end of tubular shaft 8 which faces pinion 2 is in one with a circular plate 14 which carries three longitudinally directed pins 15. Pins 15 are slidably engaged into corresponding bores provided in a sleeve 16 which is rotatably and slidably mounted on shaft 1 by means of linings 17. This sleeve 16 has a single lateral clutch tooth 16a which extends angularly through substantially 180, the lateral sides of this tooth being very slightly oblique as shown. This tooth 16a is adapted to cooperate with a similar tooth 2a provided at the rear end of pinion 2.

It will be understood that when sleeve 16 is pushed towards the right in FIG. 1, teeth 16a and 2a are in mutual engagement and tubular shaft 8, which is driven by the loom, in turn drives pinion 2 through the said sleeve. The jacquard is thus connected, with the loom. If on the contrary sleeve 16 is displaced towards the left, teeth 16a and 2a are disengaged and shaft 8 rotates without driving pinion 2. The jacquard is de-clutched from the loom.

In order to displace sleeve 16 axially, the latter is formed with a peripheral groove 16b which receives rollers carried by the branches of a conventional fork 18 pivotally mounted on a lateral support (not illustrated). One of the branches of this fork has an outer follower roller 19 which is engaged into the profiled groove 20a of a cylindrical cam 20 mounted on an auxiliary driving shaft 21. Shaft 21 is parallel to the main shaft 1 and it is rotatably supported and axially retained by friction bearings 22 and 23 carried by frame parts 6 and 7. It is to be remarked that cam 20 is slidably keyed on shaft 21 by a key 24, its axial position being adjusted by means of a screw 25 having a flat annular skirt 25a which is engaged into a circular groove of shaft 21. It will be understood that when shaft 21 is rotated, cam 20 may thus effect longitudinal control of sleeve 16 on shaft 1.

1n the vicinity of its left-hand end shaft 1 has keyed thereon a sleeve 27 provided with a large number of lateral triangular teeth directed towards the adjacent end of the shaft and which have been referenced 27a in FIGS. 4 and 5. These teeth are adapted to cooperate with similar teeth 28a carried by a sleeve 28 which is rotatably and slidably supported by the end of shaft 1 by means of a lining 29. A pinion 30, the particular construction of which will be described later with reference to FIG. 3, is affixed against the left-hand side of sleeve 28 in FIG. 1. This pinion cooperates with a gear wheel 31, also of particular construction, which is secured against the left-hand side of a cylindrical cam 32 carried by the auxiliary driving shaft 21. As cam 20, cam 32 is slidably keyed on shaft 21 and its axial position may be adjusted by means of a screw 34 having a flat circular skirt 35 engaged into a groove 21b of the said shaft. Cam 32 is formed with a profiled peripheral groove 36 which receives a follower roller 37 carried by one of the branches of a fork 38 adapted to cooperate with a groove 28b of sleeve 28 in order to control the axial position of the latter. FIG. 3 clearly shows the arrangement of fork 38 with its lateral pivot, as conventional in the art. It is to be noted in this respect that the representation of FIG. 3 may be considered, if desired, as

also corresponding to the general arrangement of above-mentioned fork 18.

Cam 32 carries on its right-hand side a gear wheel 39 which is connected through a speed-reducing gearing, with an individual driving motor combined with an automatic brake. Since these elements form no part of the device proper, they have been merely indicated in broken lines as comprising the electric motor proper 40 with the automatic brake (not shown) incorporated therein in the conventional manner, a first pinion 41 on the motor shaft, a first gear wheel 42 in mesh with pinion 41, a second pinion 43 rotated by gear 42, a second gear wheel 44, a third pinion 45, a third gear wheel 46 and finally a fourth pinion 47 in mesh with the above mentioned gear wheel 39.

As illustrated in FIG. 3 gear wheel 31 comprises a toothed sector 31a extending through one half of its periphery, the other half being in the form of a smooth sector 31b of somewhat smaller radius. Depressions 31c are provided in sector 31b at both ends thereof, i.e. where it joins sector 31a. Pinion 30 also comprises a toothed sector 30a adapted to mesh with sector 31a, but which extends through the major portion of the periphery of pinion 30, the remainder being equipped with a relatively wide protruding tooth 30b the outer edge of which is in the form of a concave depression so as to fit against the smooth sector 31b.

The length of the toothed sector 31a of gear wheel 31 is equal to the length of the toothed sector 30a of pinion 30. If therefore shaft 21 is rotated starting form the position of FIG. 3, at which tooth 30b is situated midway of the ends of sector 31b, during substantially a first rotation of of wheel 31 pinion 30remains blocked by the engagement of sector 31b into the concavity of tooth 30b, then the first tooth of sector 31a comes into contact with tooth 30b which, owing to the presence of the adjacent depression 31c is no more prevented from rotating. Toothed sectors 31a and 30a thus come into mesh and during the next of rotation of shaft 21 pinion 30 will effect almost a full revolution. Then tooth 30b will enter the other depression 31: and its concavity will again fit against the smooth periphery of sector 31b. Pinion 30 will then have effected one complete revolution.

Gear wheel 31 carries on its left-hand side in FIG. 1 a finger 48 adapted to cooperate with a micro-switch 49 in order to stop the auxiliary motor 40 when shaft 21 has effected a full revolution.

It will further be remarked that a recess 28c (FIG. 5) is provided in the toothed portion of sleeve 28. This recess receives a slidable head 50 (see also FIG. 4) which carries a centering tooth 50a. Head 50 has a tail portion 50b which slides in a longitudinal bore 28d of sleeve 28, its free end receiving the action of a compression spring 51 housed in an aperture of pinion 30 where it rests against an adjusting screw 52. A washer 53 limits the displacement of tail 50b under the action of spring 51. At the position of rest (FIGS. 4 and 5) the centering tooth 50a protrudes somewhat beyond the other teeth 28a of sleeve 28 and it is very slightly displaced (downwardly in FIG. 5) with respect to these other teeth.

The device described operates as follows During normal operation of the loom sleeve 16 is applied towards the right against pinion 2, as illustrated in FIG. 1, and it is therefore angularly connected with the said pinion by teeth 16a and 2a. On the contrary sleeve 28 is fully disengaged from sleeve 27. The tubular shaft 8, positively driven by the loom through sprocket 12 and chain 13, therefore drives the jacquard through pins 15, sleeve 16, pinion 2 and bevel wheel 3.

When the operator stops the loom, the latter is blocked and retained at standstill by an automatic brake which is generally combined with the loom driving motor itself. Tubular shaft 8 is thus prevented from rotating.

If now the jacquard is to be rotated forward or backward independently of the loom, the individual auxiliary motor 40 should be arranged to rotate in the proper direction. For instance, and as shown in FIG. 6, there may be provided for this ur ose an electromagnetically actuated reversing switch 54 with two controlling buttons 55 and 56 for one and the other direction, the above-mentioned micro-switch 49 (which is open at rest by finger 48, see FIG. 3) being inserted in the selfretaining circuit of switch 54.

As soon as the operator depresses the proper one of buttons 55 and 56, motor 40 starts in the desired direction and finger 48 liberates micro-switch 49 which closes. The operator may therefore release the button, the reversing switch being automatically retained until shaft 21 and gear wheel 31 have completed a full revolution.

This full revolution of wheel 31 may be divided into three steps:

During a first step (90) the smooth sector 31b slides against the depressed outer edge of tooth 30b, whereby pinion 30 remains blocked against any angular displacement. But during this step cam 20 displaces sleeve 16 towards the left so as to disengage same form pinion 2, while at the same time cam 32 displaces sleeve 28 towards the right so as to bring it into engagement with sleeve 27. This of course entails a slight axial displacement of pinion 30 with respect to wheel 31, but both are provided wide enough for this purpose. At the end of this first operative step pinion 2 and shaft 1 are de-clutched form tubular shaft 8 and are on the contrary clutched with pinion 30. Since the latter is still blocked by wheel 31, shaft 1 and the jacquard are prevented from rotating. It is important to note that there is no intermediate dead position between the disengagement of sleeve 16 from pinion 2 and the engagement of sleeve 28 with sleeve 27, both operations taking place simultaneously. Shaft l is at no time free to rotate. Screws 25 and 34 besides permit an accurate adjustment of the axial displacement of sleeves l6 and 28.

During a second step (180) the toothed sector 3 la of wheel 31 drives the toothed sector 30a of pinion 30 which effects a full rotation together with shaft 1 itself. Things are so arranged that this revolution corresponds to one full cycle of the jacquard (i.e. one pick forward or backward).

Finally during a third step (90) the operations are the same as for the first step, but in the reverse direction, that is to say that sleeve 28 becomes disengaged from sleeve 27 while sleeve 16 is engaged with pinion 2, without any intermediate dead osition during which the jacquard might be free to rotate.

When wheel 31 has completed its revolution finger 48 opens micro-switch 49 and stops motor 40. The parts have resumed their initial position and the operator may therefore either depress button 55 or 56 to re-start motor 40 and to again cause the jacquard to rotate through a full cycle or pick either forward or backward, or resume normal operation of the loom.

The slight inclination or obliquity of the edges of teeth 16a and 20 has for its result that during the disengagement and the re-engagement pinion 2 and shaft 1 may rotate slightly in order to avoid any jamming either when sleeve 27 engages sleeve 28 or when sleeve 16 engages pinion 2. The angle of obliquity should correspond to the obliquity of teeth 27a and 28a, i.e. to half the pitch of these teeth. When this condition is fulfilled, sleeve 28 may slightly rotate to permit its full engagement with sleeve 27 when sleeve 16 is becoming disengaged from pinion 2, or conversely to permit full engagement of sleeve 16 with pinion 2 when sleeve 28 is becoming disengaged from sleeve 27.

It may occur that when sleeve 28 is being displaced towards sleeve 27, teeth 27a and 280 are exactly facing each other. Under such conditions the slightest error in the cutting of these teeth could cause jamming, a tooth 28a tending to slide for instance against the upper edge of the facing tooth 27a in FIG. 5, while another tooth 28a would tend to slide against the lower edge of another tooth 27a. The centering tooth 50a has for its object to avoid such a difficulty. This tooth 50a, carried by sleeve 28, comes into contact with a tooth 27a of sleeve 27 before the other teeth 28a of sleeve 28, and it may freely cause a relative rotation between sleeves 27 and 28 without this being hindered by a tooth 28a. When the teeth 28a engage teeth 27a there is no possibility therefore of their tips abutting. against the tips of teeth 270. As above indicated, tooth 50a is very slightly displaced angularly with respect toteeth 28min such manner that if its tip occurred to remain against the tip of a tooth 27a, the teeth 28a would certainly slide against the same side of teeth 27a and thus cause disengagement of tooth 50a.

It will be understood that the speed-reducing gearing interposed between motor 40 and shaft 21 may be of any construction, as for instance of the worm-and-wheel type, which would afford the advantage of being irreversible. The cams carried by the auxiliary driving shaft 21 could be of any type and they could actuate sleeves l6 and 28 through any kind of intermediate gearing such as levers, rods or the like. The blocking in rotation of shaft 21 could be effected by a brake separate from motor 40, but controlled by the same electric circuitry.

l CLAIM 1. A device to be inserted between a loom and the shedforming mechanism thereof, comprising a main shaft adapted to be positively connected with the shed-forming mechanism to drive same, said main shaft effecting one complete revolution for each operative cycle of said mechanism a rotating member adapted to be positively connected with the loom so as to effect one complete revolution for each pick thereof clutch means to connect said main shaft with said rotating member during normal weaving operation of the loorn, said clutch means being so arranged as to insure a predetermined angular relation between said rotating member and said main shaft;

coupling means carried by said main shaft and including a first element angularly secured to said main shaft and a second element loosely mounted thereon, said first and second elements being engageable with and disengageable from each other;

an auxiliary driving shaft to rotate the second element of said coupling means, said auxiliary driving shaft being adapted to be rotated at a slow speed by successive full revolutions in one or the other direction gearing means to connect said auxiliary driving shaft with the second element of said coupling means, said gearing means being so arranged that during a first portion of one revolution of said auxiliary driving shaft said second element is blocked angularly, that during a second portion of said one revolution said second element is rotated through a complete revolution, and that during a third and last portion of said one revolution of said auxiliary driving shaft said second element is again blocked angularly and cam means on said auxiliary driving shaft to control said clutch means and said coupling means so as to derclutch said main shaft from said rotating member while engaging said second element of said coupling means with said first element thereof during said first portion of one revolution of said auxiliary driving shaft, and to again clutch said main shaft with said rotating member while disengaging said second element of said coupling means form said first element thereof during said third portion of one revolution of said auxiliary driving shaft. 2. IN a device as claimed in claim 1, said rotating member being in the form of a tubular shaft rotatably carried by said main shaft.

3. In a device as claimed in claim 1, said clutch means embodying two rotatable members each including a single tooth extending through substantially about said main shaft and having oblique lateral sides each extending through a pre-determined angle about said main shaft and said elements of said coupling means each including a multiplicity of substantially triangular teeth 7 with the oblique sides of said teeth each extending about said main shaft through an angle substantially equal to said predetermined angle.

4. In a device as claimed in claim 1, said gearing means comprising a first toothed sector carried by said auxiliary driving shaft and extending substantially through 180 a blocking sector with smooth periphery also carried by said auxiliary driving shaft and extending substantially through the l80 unoccupied by said toothed sector a second toothed sector carried by said second element of said coupling means to cooperate with said first toothed sector, said second toothed sector having the same length as said first sector, but being of smaller radius so as to leave between its ends an angular space smaller than 180 and a blocking tooth carried by said second element of said coupling means in the angular space left between the ends of said second toothed sector, said blocking tooth having an upper edge formed with a concave depression to cooperate with the smooth periphery of said blocking sector so as to prevent said second element form rotating until said smooth periphery is disengaged from said concave depression during rotation of said auxiliary driving shaft.

5. In a device as claimed in claim 4, one of said elements of said coupling means having a longitudinally slidable triangular tooth and spring means urging said tooth to protrude beyond the other triangular teeth of said one of said elements, so that said longitudinally slidable tooth may engage the triangular teeth of the other one of said elements before the other teeth of said one of said elements.

6. In a device as claimed in claim 5, said slidable tooth being slightly displaced angularly on said one of said elements with respect to the other teeth thereof.

7. In a device as claimed in claim 1, each of said clutch means and coupling means including an axially movable element and said cam means comprising for each of said movable elements a cylindrical cam carried by said auxiliary driving shaft, said cylindrical cam having a profiled groove, a pivoted fork embracing said each of said movable elements with same having a circular groove to receive said fork, and a follower carried by said fork and engaged into the profiled groove of said cylindrical cam.

8. In a device as claimed in claim 1,

an electric motor with automatic braking means to rotate said auxiliary driving shaft speed-reducing means to connect said motor with said auxiliary driving shaft a switch to stop rotation of said motor and cam means carried by said auxiliary driving shaft to actuate said switch and to stop said motor whenever said auxiliary driving shaft has effected a full revolution. 

1. A device to be inserted between a loom and the shed-forming mechanism thereof, comprising : a main shaft adapted to be positively connected with the shedforming mechanism to drive same, said main shaft effecting one complete revolution for each operative cycle of said mechanism ; a rotating member adapted to be positively connected with the loom so as to effect one complete revolution for each pick thereof ; clutch means to connect said main shaft with said rotating member during normal weaving operation of the loom, said clutch means being so arranged as to insure a pre-determined angular relation between said rotating member and said main shaft; coupling means carried by said main shaft and including a first element angularly secured to said main shaft and a second element loosely mounted thereon, said first and second elements being engageable with and disengageable from each other; an auxiliary driving shaft to rotate the second element of said coupling means, said auxiliary driving shaft being adapted to be rotated at a slow speed by successive full revolutions in one or the other direction ; gearing means to connect said auxiliary driving shaft with the second element of said coupling means, said gearing means being so arranged that during a first portion of one revolution of said auxiliary driving shaft said second element is blocked angularly, that during a second portion of said one revolution said second element is rotated through a complete revolution, and that during a third and last portion of said one revolution of said auxiliary driving shaft said second element is again blocked angularly ; and cam means on said auxiliary driving shaft to control said clutch means and said coupling means so as to de-clutch said main shaft from said rotating member while engaging said second element of said coupling means with said first element thereof during said first portion of one revolution of said auxiliary driving shaft, and to again clutch said main shaft with said rotating member while disengaging said second element of said coupling means form said first element thereof during said third portion of one revolution of said auxiliary driving shaft.
 2. IN a device as claimed in claim 1, said rotating member being in the form of a tubular shaft rotatably carried by said main shaft.
 3. In a device as claimed in claim 1, said clutch means embodying two rotatable members each including a single tooth extending through substantially 180* about said main shaft and having oblique lateral sides each extending through a pre-determined angle about said main shaft ; and said elements of said coupling means each including a multiplicity of substantially triangular teeth with the oblique sides of said teeth each extending about said main shaft through an angle substantially equal to said pre-determined angle.
 4. In a device as claimed in claim 1, said gearing means comprising a first toothed sector carried by said auxiliary driving shaft and extending substantially through 180* ; a blockIng sector with smooth periphery also carried by said auxiliary driving shaft and extending substantially through the 180* unoccupied by said toothed sector ; a second toothed sector carried by said second element of said coupling means to cooperate with said first toothed sector, said second toothed sector having the same length as said first sector, but being of smaller radius so as to leave between its ends an angular space smaller than 180* ; and a blocking tooth carried by said second element of said coupling means in the angular space left between the ends of said second toothed sector, said blocking tooth having an upper edge formed with a concave depression to cooperate with the smooth periphery of said blocking sector so as to prevent said second element form rotating until said smooth periphery is disengaged from said concave depression during rotation of said auxiliary driving shaft.
 5. In a device as claimed in claim 4, one of said elements of said coupling means having a longitudinally slidable triangular tooth and spring means urging said tooth to protrude beyond the other triangular teeth of said one of said elements, so that said longitudinally slidable tooth may engage the triangular teeth of the other one of said elements before the other teeth of said one of said elements.
 6. In a device as claimed in claim 5, said slidable tooth being slightly displaced angularly on said one of said elements with respect to the other teeth thereof.
 7. In a device as claimed in claim 1, each of said clutch means and coupling means including an axially movable element and said cam means comprising for each of said movable elements a cylindrical cam carried by said auxiliary driving shaft, said cylindrical cam having a profiled groove, a pivoted fork embracing said each of said movable elements with same having a circular groove to receive said fork, and a follower carried by said fork and engaged into the profiled groove of said cylindrical cam.
 8. In a device as claimed in claim 1, an electric motor with automatic braking means to rotate said auxiliary driving shaft ; speed-reducing means to connect said motor with said auxiliary driving shaft ; a switch to stop rotation of said motor ; and cam means carried by said auxiliary driving shaft to actuate said switch and to stop said motor whenever said auxiliary driving shaft has effected a full revolution. 